1. Technical Field of the Invention
The present invention relates to the field of integrated circuits, and more particularly to integrated circuits comprising one or more acoustic or piezoelectric resonators. Such circuits can be used in signal processing applications, for example, for performing a filtering function.
2. Description of Related Art
Acoustic resonators are integral with the integrated circuit, while having to be acoustically or mechanically isolated therefrom. For this purpose, a support capable of producing such isolation may be provided. The support may comprise an alternation of a layer having a high acoustic impedance and a layer having a low acoustic impedance (see, U.S. Pat. No. 6,081,171, the disclosure of which is hereby incorporated by reference).
The term “acoustic impedance” is understood to mean the quantity Z given by the density ρ of the material multiplied by the acoustic velocity ν, i.e., Z=ρν. The acoustic velocity ν may be taken as being defined by:ν=(ρC33)1/2where C33 is one of the coefficients of the elastic compliance matrix.
For high acoustic isolation performance, it is desirable for the difference in acoustic impedance between the materials to be as high as possible.
A need exists in the art to meet this requirement.